As is well known, since the government has lifted the price on gold from $35.00 an ounce, the price of gold has multiplied. As a result, many gold mines which were forced out of operation by the $35.00 an ounce ceiling have now resumed operations, and gold exploration and mining has greatly increased.
Because most gold ores contain less than a few ounces of gold per ton of ore, large amounts of gangue must be processed in order to recover the gold. In addition to the low grade of gold ores, the gold is usually present as very fine particles. Thus, gravity processes for the separation of gold from gangue are inefficient. This is due to the high viscous drag forces acting on small particles in water relative to the force of gravity.
Typically, large amounts of water are needed for beneficiating gold ores, particularly placer gold ores. This is a significant problem in recovering gold from low grade ores particularly placers existing in arid areas such as deserts. There is, therefore, considerable time and expense involved in recovering gold from its ores.
The above conditions have created a need for improved and more efficient beneficiating procedures for the recovery of gold from low grade ores, i.e., gold associated with foreign materials with which the gold exists in small percentages. Also, a process which operates dry would be especially useful, because it would provide a method for recovering gold which is located in deserts.
Accordingly, it is a principal object of this invention to provide an economically feasible method for separating gold from foreign material by selectively enhancing the magnetic susceptibility of the gold particles so that they may be successfully separated from the foreign material by magnetic separation.